1. Field of the Invention
The invention relates to a vehicle network system and a vehicle information processing method that uses the network system.
2. Description of Related Art
In a vehicle network system, a plurality of electronic control units (ECUs) each are connected to a network. Then, pieces of information in the respective ECUs are exchangeable among the ECUs.
Then, for each of the ECUs network-connected to the above vehicle network system, work for maintenance and update of a program of the ECU is often carried out via a maintenance device, such as a tester, externally connected to the vehicle network. That is, the program of the ECU is updated through rewriting, that is, reprogrammed, through the maintenance device connected to the vehicle network.
On the other hand, the program contents of each network-connected ECU may be changed via the network. That is, a program of such an ECU may be tampered through, for example, reprogramming improperly executed by a maintenance device illegally connected to the network or may be tampered through unauthorized access to the network by some means. Then, there has been suggested a system that detects whether a program of an ECU connected to a vehicle network has been tampered, and one example of the system is described in Japanese Patent Application Publication No. 2005-242871 (JP 2005-242871 A).
In the system described in JP 2005-242871 A, a plurality of ECUs and one gateway are connected to a vehicle network so as to be communicable with one another. Each ECU transmits a hash value of data incorporated in itself to the gateway as an ignition switch (IG) is turned off. Upon receiving the hash value, the gateway stores the transmitted hash value of each ECU as comparison data in an EEPROM. On the other hand, when each ECU starts operation as the IG is turned on, each ECU transmits the hash value of data incorporated in itself to the gateway. By so doing, the gateway compares the transmitted hash value with the corresponding comparison data stored in the EEPROM for each ECU. Then, when a mismatch occurs between the transmitted hash value and the corresponding comparison data, the gateway determines that the data of that ECU has been tampered.
Resistance against tampering (tamper resistance) with a device that determines whether data has been tampered as described above and each ECU itself is desired. Therefore, it has been studied that, for example, a tamper-resistant memory is employed in those devices. However, if such a memory is employed, it is complicated for the vehicle network system to handle data, including reprogramming, and the like, and it is unavoidable to increase the cost of the vehicle network system due to usage of an expensive memory.